The present invention relates generally to cathode ray tubes, and more particularly to a cathode ray tube incorporating a deflection yoke with a horizontal deflection coil disposed on a saddle type mold die.
An important aspect of performance for a television monitor is its ability to correctly align the individual color components projected onto the screen of the monitor (e.g., red, green and blue). Convergence describes how far apart the three electron beams spread from one another within a pixel in a CRT. In an ideal situation, the beam strikes all three dots without hitting any adjacent groups. Mis-convergence is a quantitative measurement of the lack of proper convergence of the three electron beams. Where mis-convergence occurs, the resulting image will have a shadowed appearance.
A deflection yoke is used to control the convergence of the three electron beams (e.g., red, green and blue) in a Cathode Ray Tube (CRT) by altering the winding distribution in the horizontal and vertical coils to compensate for mis-convergence. For example, U.S. Pat. No. 5,838,099 discloses one such deflection yoke.
There are several patterns related to mis-conversion in CRTs. Examples are XH, HCR, PQV, PQH, S3V and Top/Bottom Pin. These are the key parameters for a Horizontal Coil.
Referring to FIGS. 1A through 1E, depicted therein are various patterns of mis-convergence. In FIG. 1A, the mis-convergence is referred to as XH mis-convergence. In XH mis-convergence, the plus patterns of the red (R) and blue (B) lines fail to converge. FIG. 1B shows HCR mis-convergence. In HCR mis-convergence, the plus patterns of the green (G) line fail to converge with the plus patterns of the of the red (R) and blue (B) converged lines. FIG. 1C shows PQV mis-convergence. In PQV mis-convergence, the red (R) and blue (B) lines fail to converge horizontally at the vertical extents of the CRT as shown. FIG. 1D shows PQH mis-convergence. In PQH mis-convergence, the red (R) and blue (B) lines fail to converge in convex fashion at the horizontal extents of the CRT as shown. FIG. 1E shows S3V mis-convergence. In this pattern, the red (R) and blue (B) lines do not converge as shown. FIG. 1F shows a pattern of geometry known as Top/Bottom Pin. In this pattern, geometry occurs as a xe2x80x9cbowingxe2x80x9d of the green (G) lines (and of course red and blue lines) at the vertical extents of the CRT.
Normally, mis-convergences are resolved by the deflection Yoke (DY) itself. A Horizontal deflection coil has a Pin-cushion magnetic field and a Vertical coil has a Barrel magnetic field. Each of these magnetic fields yields one or more of the patterns shown in FIGS. 1A thru 1F. In the manufacture of Vertical and Horizontal coils the target objective is to attain zero values for each of the patterns of mis-convergence; i.e., XH=0, HCR=0, PQV=0, PQH=0, S3V=0 and Top/Bottom pin=0.
Heretofore, it has been possible to adjust for mis-convergence in CRTs by changing the winding distribution on Horizontal and Vertical coils. With the advent of the larger screen sizes being produced today and their corresponding wide deflection angles and flat profiles, adjusting for mis-convergence by traditional methods is more difficult.
One attempt to correct deflection mis-convergence requires extra corrective parts on the deflection yoke. For example, U.S. Pat. No. 5,142,205 discloses a deflection yoke having a correction circuit for correcting horizontal and vertical mis-convergence. This technique requires additional electrical components, thereby resulting in increased parts content and assembly costs of the CRT being manufactured. Moreover, the dimensions of the resulting device are increased as a result of the additional parts installed.
Alternatively, the Horizontal coil of the CRT can be re-manufactured in an attempt to simultaneously reduce the mis-convergence phenomena. However, this process is unwieldy and inefficient in a fast assembly process.
The present invention is therefore directed to the problem of developing method and apparatus for adjusting mis-convergence patterns in a CRT, which method and apparatus is suitable for application to a rapid and existing assembly process used to manufacture larger and flatter CRT screens without increasing the cost of manufacture, or size of the device.
The present invention solves these and other problems by creating a depression in the windings of the horizontal coil at a predetermined location. In particular, the present invention provides a depression in the windings of a horizontal deflection coil of a CRT in a xe2x80x9cneckxe2x80x9d portion of the deflection yoke, which incorporates a horizontal deflection coil disposed on a saddle type mold die.
According to one aspect of the present invention, a deflection yoke for deflecting electron beams of a color CRT includes a horizontal deflection coil disposed on a saddle type mold die has a funnel section and a neck section connected along a horizontal axis parallel to the centerline of the deflection yoke. A portion of the neck section of the deflection yoke includes an offset relative to the profile (relative to the horizontal axis) of the windings of the horizontal coil that creates a depressed area in the windings of the horizontal deflection coil.
According to another aspect of the invention, in the above deflection yoke, the disposition angle of the horizontal deflection coil relative to the horizontal axis in the neck portion of the depressed area lies within a range between approximately 40 degrees and approximately 60 degrees.
According to another aspect of the invention, in the above deflection yoke the disposition angle of the horizontal deflection coil relative to the horizontal axis in the funnel portion of the depressed area lies within a range between approximately 30 degrees and approximately 45 degrees.
According to yet another aspect of the present invention, in the above deflection yoke, a depth of the offset lies within a range between approximately 0.5 millimeters and approximately 1.0 millimeters.
According to yet another aspect of the present invention, in the above deflection yoke, the mold die assembly comprises a Pin shoot coil winding assembly.
According to another aspect of the present invention, in the above deflection yoke, the depression in the windings of the horizontal deflection coil occurs at a predetermined distance from a beginning of the neck section of the deflection yoke assembly along the horizontal axis through the neck section and funnel sections of the deflection yoke.
According to another aspect of the present invention, a method for simultaneously correcting multiple types of mis-convergence in a deflection yoke of a cathode ray tube having a neck section and a funnel section and a horizontal deflection coil disposed between the neck and funnel section on a saddle type mold die, comprises the following steps. Firstly, a location is selected in the length of the deflection yoke along the horizontal distance between the neck section and the funnel section by dividing said length into four substantially equal sections. Secondly, in a second section of the four substantially equal sections taken from the neck side, along the horizontal axis connecting the neck side to the funnel side, a depression is formed in the windings of the horizontal deflection coil, said depression is relative to the horizontal axis between the neck and funnel sections of the deflection yoke. The depression in the windings creates interference patterns in the electronic fields induced by the horizontal deflection coil that eliminates the multiple types of mis-convergence.
According to another aspect of the present invention, in the above method, the depressed area created in the windings of the horizontal deflection coil is quadrangle shaped.
According to another aspect of the present invention, a device for simultaneously correcting multiple types of mis-convergence includes a deflection yoke further comprising a mold die assembly with a horizontal deflection coil disposed thereon. The deflection yoke is symmetrical about a horizontal axis and has a neck section and funnel section. The profile of the horizontal deflection coil of the deflection yoke is depressed in a portion of the neck section, creating a correction for the mis-convergence of the electron beams in a CRT.
According to another aspect of the present invention, in the above device, the depression in the windings of the horizontal deflection coil is disposed at a predetermined distance from the beginning of the neck section along a horizontal axis between the neck and funnel sections, in the direction of the funnel section.
According to another aspect of the invention, in the above device, the location of the offset is predetermined by first dividing the length of the deflection yoke along the horizontal distance between the neck section and the funnel section into four equal sections and selecting the second section as the area over which to depress the windings of the horizontal deflection coil.